If N. Korea is the Threat, Why is all the War Talk about a Weak Iran?

All the talk in Washington is about war on Iran, which poses no threat to the United States. But one never hears belligerence toward North Korea, which routinely menaces the US (most recently threatening to nuke the US territory of Guam). In contrast, Iran’s Supreme Leader Ali Khamenei has said his country cannot have nuclear weapons because they are incompatible with Islamic law (which forbids killing innocent noncombatants).